1) Field of the Invention
The present invention relates to an activation device for a passenger protection apparatus to be mounted in a vehicle, and more particularly to a technique for activating a passenger protection apparatus at an appropriate timing in response to the occurrence of a roll (rollover) of a vehicle.
2) Description of the Related Art
So far, as a vehicle-mounted passenger protection apparatus for protecting a passenger(s) (including a driver) from the occurrence of a roll of a vehicle, for example, there have been proposed a curtain air bag designed to spread into a curtain-like configuration along a side surface portion of the vehicle, a seat belt with a pretensioner made to take up a seat belt in no time, and an apparatus made to take up a seat belt in a repeated fashion through the use of a motor or the like.
For example, as shown in a block diagram of FIG. 8, a conventional activation system 51 for a passenger protection apparatus is made up of an angular velocity sensor 61 for detecting a roll angular velocity of a vehicle, a control unit 80 including a CPU 80a, a ROM 80b and a RAM 80c, and a curtain air bag 90. When the angular velocity sensor 61 outputs a roll angular velocity signal, a relative angle calculating means 81 makes an integral calculation of a roll angular velocity to obtain a roll relative angle, and a roll judging means 83 makes a decision that the vehicle rolls sideways if the roll angular velocity and the roll relative angle exceed a predetermined condition, and then a drive control means 84 activates a curtain air bag 90.
However, among rolls of a vehicle, there are diverse modes and, in some modes, there should be a need to make a judgment on a roll of a vehicle at an earlier stage. For example, if a vehicle does a sideslip to make its tire(s) collide against a curb stone on a road, a large impact acceleration and a large angular velocity occur, which can increase a rolling speed rapidly to lead to a roll of the vehicle. In the case of such a roll of the so-called trip-over type, since a passenger(s) existing on a seat is shifted toward the exterior of the vehicle body (a door side) due to an inertia when the tire collides against the curb stone or the like to decrease the sideslip speed, there is a possibility of hindering a smooth spread of a curtain air bag taking place along a side surface portion of the vehicle. On the other hand, also in the case of a seat belt with a pretensioner or an apparatus made to take up a seat belt in a repeated fashion through the use of a motor or the like, not until the seat belt is taken up at an early stage, the throw-out of a passenger into the exterior of the vehicle or the collision thereof against an internal member of the motor vehicle is effectively preventable.
Therefore, in a case in which a tire collides against a curb stone or the like, or in a like situation, there is a need to detect the occurrence of the trip-over type roll earlier for quickly operating a passenger protection device, such as a curtain air bag, a seat belt with a pretentioner and an apparatus made to take up a seat belt in a repeated fashion through the use of a motor or the like.